We have 3 3 phase 3 HP fan motors that are continuous duty. Can we use cord and plug and the breaker to operate the motors? or do we have to use a overload section on each motor?
Most 3 phase motors do not have built in overload protection. You have to install an overload device in each conductor & this is usually done with a motor starter. See 430.32
As for using the cord & plug connection, that will require a horsepower rated receptacle and a horsepower rated cord cap.430.109(F)
Tom
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